Hearing loss characteristics are highly individual and hearing thresholds vary substantially from person to person. The hearing loss varies from frequency to frequency, which is typically reflected by a clinical audiogram. Depending on the type and severity of hearing loss (sensorineural, conductive or mixed; light, moderate, severe or profound), the sound processing features of the human ear are compromised in different ways and require different types of functional intervention, from simple amplification of incoming sound as in conductive hearing losses to more sophisticated sound processing and/or using non-acoustic transducers as in the case of profound sensorineural hearing losses.
Hearing devices or aids are often employed to address hearing deficiencies. Conventional hearing aids capture incoming acoustic signals, amplify the signals and output the signal through a loudspeaker placed in the external ear channel. In conductive and mixed hearing losses an alternative stimulation pathway through bone conduction or direct driving of the ossicular chain or the inner ear fluids can be applied via bone conductive implants or middle ear implants.
Bone conductive implants aids resemble conventional acoustic hearing aids, but transmit the sound signal through a vibrator to the skull of the hearing impaired user. Middle ear implants use mechanical transducers to directly stimulate the middle or the inner ear.
In sensorineural hearing losses deficits in sound processing in the inner ear result in an altered perception of loudness and decreased frequency resolution. For example, to compensate for the changes in loudness perception less amplification is typically provided for high-level sounds than for low-level sounds.
The core functionality of hearing aids in sensorineural hearing losses is thus (a) compensating for the sensitivity loss of the impaired human ear by providing the required amount of amplification at each frequency and (b) compensating for loudness recruitment by means of a situation dependent amplification.
In profound sensorineural hearing losses the only functional solution for the patients can be offered by cochlear implants (CI). Cochlear implants provide electric stimulation to the receptors and nerves in the human inner ear.
In the signal processing chain of a cochlear implant, the signal that is received by the microphone is processed in a similar fashion as in a hearing aid. A second stage then transforms the optimized sound signal into an excitation pattern for the implanted stimulator.
The core task of signal processing of hearing aids and an important part in the signal pre-processing of other hearing support systems comprises frequency-equalization filtering and amplification, as well as automatic gain control to provide the appropriate amount of loudness perception in all listening situations. In addition to these core tasks, the signal processing can, and often does, provide noise reduction, feedback reduction, sound quality enhancements, speech intelligibility enhancements, improved signal-to-noise ratio of sounds from specific directions (directional microphones, beam forming) and more.
Hearing aids and other hearing solutions not only need to modulate amplification to the individual hearing loss of the patient, but ideally also need to modulate the amount of amplification to the current sound environment. This is related to the phenomenon of loudness recruitment that is characteristic for sensorineural hearing losses.
As a result of loudness recruitment, greater amplification is typically required in soft listening situations than in loud listening situations. A slow adaptation of the amount of amplification to the sound environment, with time constants greater than 1 sec., is often referred to as “automatic volume control”. The noted adaptation has the advantage of providing the correct amount of amplification without distorting the signal.
However, abrupt changes in the level of the input signal are usually not compensated for and can, and in many instances will, result in a painful sensation or the loss of important information that follows a loud event. Exemplar abrupt changes include sudden loud sounds (door bang), but they also occur when listening to two people talking simultaneously with one of the two persons being closer than the other.
The state-of-the-art approach to compensate for sudden changes in the input signal level is referred to as “automatic gain control” that employs short time constants. However, automatic gain control, i.e. fast changes of the signal amplitude, often cause a reduction of the audio quality.
Another drawback of prior art technology is that due to the necessity of custom hardware and custom chip development, most hearing aids are quite expensive. Further, hearing aids typically require specialized experts for parameter adjustments (hearing aid fitting). This fitting is typically performed by trained professionals like audiologists or ENT (ear, nose and throat) doctors on a PC with dedicated fitting software, which is normally provided by the manufacturer of the corresponding devices. Specialized expert knowledge is absolutely required to correctly adjust the parameters.
A further drawback of prior art technology is that digital hearing aids only allow a very limited number of manual adjustments by the hearing impaired person him/herself, i.e. the output volume control and, in some instances, the selection of one of a small number of predefined listening programs. Each of these programs comprises a set of parameters optimized for a specific listening situation.
In some instances, means are provided to control a hearing aid by a physical remote control (a hand held device or a wrist watch with remote control functionality), but the number of parameters that can be changed by these remote controls is limited.
Another drawback of prior art hearing aids and cochlear implants is that solutions to connect these devices to consumer electronics (TV, stereo, MP3 player, mobile phones) are cumbersome and expensive. Furthermore, conventional hearing aids are devoid of any means to connect the hearing aid to the Internet® and, if capable of communicating with Personal Digital Assistant (PDA) devices and mobile phones, the interaction is typically limited to the amplification of the voice signal during phone calls or the amplification of reproduced music.
Further, the software (firmware) that is typically employed in hearing aids is not upgradable. For a small number of hearing aids, firmware updates may be available, but these updates are not available on a frequent basis and, therefore, modifications to the signal processing are, in most instances, limited to parameter-based changes that have been anticipated when the device was manufactured.
The latest generation of state-of-the-art digital devices can allow for a simple communication between devices disposed in the left and right ear. However, this communication is limited to a low bit rate transfer of parameters, for example to synchronize parameters of the automatic gain control to avoid disturbing the spatial perception due to independent gains in the two devices. More advanced approaches that require access to the audio signal from the microphones at the left and right ear are not feasible with current technology.
Several apparatus and methods have thus been developed to address one or more of the above referenced disadvantages and drawbacks associated with conventional hearing aids. Illustrative are the apparatus and methods disclosed in U.S. Pub. Nos. 2009/074206, 2007/098115 and 2005/135644, and U.S. Pat. Nos. 6,944,474 and 7,529,545.
In U.S. Pub. No. 2009/074206 A1 a portable assistive listening system is disclosed that includes a fully functional hearing aid and a separate handheld digital signal processing device. The signal processing device contains a programmable DSP, an ultra-wide band (UWB) transceiver for communication with the hearing aid and a user input device. The usability and overall functionality of hearing aid can purportedly be enhanced by supplementing the audio processing functions of the hearing aid with a separate DSP device.
U.S. Pub. No. 2007/098115 discloses a wireless hearing aid system and method that incorporates a traditional wireless transceiver headset and additional directional microphones to permit extension of the headset as a hearing aid. The proposed solution contains a mode selector and programmable audio filter so that the headset can be programmed with a variety of hearing aid settings that can be downloaded via the Internet® or tailored to the hearing impairment of the patient. No flexible means are, however, available to easily adjust the signal processing parameters.
U.S. Pat. Nos. 6,944,474 and 7,529,545 disclose a mobile phone and means to modulate an individual's hearing profile, i.e. a personal choice profile and induced hearing loss profile (which takes into account the environmental noise), separately or in combination, to build the basis of sound enhancement. The signal input is either a speech signal from a phone call, an audio signal that is being received through a wireless link to a computer or multimedia content stored on the phone. While the sound environment is taken into account to optimize the perception of these sound sources, the sound environment itself is not the target signal. In contrast, the amplification is optimized in order to reduce the masking effect of the environmental sounds.
U.S. Pub. No. 2005/0135644 discloses a digital cell phone with built-in hearing aid functionality is disclosed. The device comprises a digital signal processor and a hearing loss compensation module for processing digital data in accordance with a hearing loss compensation algorithm. The hearing loss compensation module can be implemented as a program executed by a microprocessor. The proposed solution also exploits the superior performance in terms of processing speed and memory of the digital cell phone as compared to a hearing aid.
According to the disclosed methodology, the wireless download capabilities of digital cell phones provide flexibility to the control and implementation of hearing aid functions. In one embodiment, the hearing compensation circuit provides level-dependent gains at frequencies where hearing loss is prominent. The incoming digitized signal is processed by a digital filter bank, whereby the received signals are split into different frequency bands. Each filter in the filter bank possesses an adequate amount of stop-band attenuation. Additionally, each filter exhibits a small time delay so that it does not interfere too much with normal speech perception (dispersion) and production.
The use of a hierarchical, interpolated finite impulse response filter bank is also proposed. The outputs of the filter bank serve as inputs to a non-linear gain table or compression module. The outputs of the gain table are added together in a summer circuit.
A volume control circuit may be provided allowing interactive adjustment of the overall signal level. It is, however, noted that the audio signal captured during a phone call is used as the main input.
A further drawback associated with the disclosed wireless system, as well as most hearing aid systems, is that the wireless networks and/or protocols that are employed to transmit signals to/from the hearing aid, such as radio frequency (RF), Bluetooth® and Zigbee®, often provide limited data transmission and are often susceptible to interference.
Various wireless networks with associated protocols have thus been developed to provide accurate and reliable means to wirelessly transmit signals to/from hearing aids. Illustrative are the wireless networks disclosed in U.S. Pat. No. 7,529,565 and U.S. Pub. Nos. 2007/009124 and 2007/0259629.
U.S. Pat. No. 7,529,565 discloses a hearing aid comprising a transceiver for communication with an external device, wherein a wireless communication protocol having a transmission protocol, link protocol, extended protocol, data protocol and audio protocol is employed. The transmission protocol is configured to control transceiver operations to provide half duplex communications over a single channel. The link protocol is configured to implement a packet transmission process to account for frame collisions on the channel.
U.S. Pub. No. 2007/0009124 discloses a wireless network for communication of binaural hearing aids with other external devices, such as a smart phone, using slow frequency hopping, wherein each data packet is transmitted in a separate slot of a TDMA frame. Each slot is also associated with a different transmission frequency, wherein the hopping sequence is calculated using the ID of the master device, the slot number and the frame number. A link management package (LMP) is sent from the master device to the slave devices in the first slot of each frame.
According to the Applicants, the system can be operated in a broadcast mode, wherein each receiver is turned on only during time slots associated with the respective receiver. The system also includes two acquisition modes for synchronization, with two different handshake protocols. Eight LMP messages are transmitted in every frame during initial acquisition, and one LMP message is transmitted in every frame once a network is established. Handshake, i.e. bi-directional message exchange, is needed both for initial acquisition and acquisition into the established network.
During acquisition, a reduced number of acquisition channels is used, with the frequency hopping scheme being applied to these acquisition channels.
U.S. Pub. No. 2007/0259629 discloses a further wireless network, wherein an ultra-wide band link is employed to transmit audio signals from a main device, such as a mobile phone, to a peripheral device, such as a hearing aid. The signals are transmitted via the ultra-wide band link in very short pulses of 1 ns or less duration, which correspond to a transmission band width of about 500 MHz.
In order to reduce power consumption, the transceivers are operated in an inter-pulse duty cycling mode. In order to better match the peak current consumption from the battery during powered-on times, a capacitive element is charged when pulses are not being transmitted or received and is then discharged to power the transceiver when pulses are being transmitted or received.
There are, however, several drawbacks associated with the noted system. A major drawback is that the hearing aid still contains a significant additional transmitter whose sole purpose is to close the communications loop. It is the essence of the present invention is to greatly simplify or completely eliminate an additional transmitter within the hearing aid.
A further drawback associated with conventional hearing aids is limited battery life. This is particularly a major issue for users of partially implantable hearing aids, wherein the power required by the implanted component of the hearing aid is supplied by a battery of the external component. Battery life time in partially implantable hearing aids typically is on the order of one day.
While the battery of the external component of the hearing aid in principle can be replaced quiet easily, a spare battery needs to be available and, depending on the situation, the user of the hearing aid may not want to a attract attention when attempting to change the battery. Further, during replacement of the battery the hearing aid does not function, so that the user, depending on the degree of his hearing loss, may be more or less deaf. In particular, such temporary deafness will be very disturbing in daily life, especially for active people.
In principle, users of conventional electro-acoustic hearing aids encounter similar problems, but to a less prominent extent, since ear battery runtimes typically are more than one week and, except for profound losses, the users of electro-acoustic hearing aids typically have a certain level of residual hearing and speech understanding without electronic amplification.
Several systems and methods have thus been developed to modulate battery use and, thereby, life. Illustrative are the apparatus and methods disclosed in U.S. Pat. No. 6,904,156 and U.S. Pub. No. 2009/0074203.
U.S. Pat. No. 6,904,156 discloses an electro acoustic hearing aid, wherein the hearing aid audio amplifier is disabled when low battery voltage is sensed.
U.S. Pub. No. 2009/0074203 discloses an electro acoustic hearing aid, which is connected via an ultra wide band (UWB) link to another hearing aid worn at the other ear and to a belt-won external processing device and. The wireless transceiver of the hearing aid is configured to power-down when low battery power is detected. The hearing aid is also switched to a conventional analog amplifier mode when the hearing aid power is critically low.
One additional drawback associated with conventional (or prior art) hearing aids is that they are often unattractive and associated with age and handicaps. (This social phenomenon is often referred to as “stigmatization”.) Even with the latest improvements of less visible devices, amongst the hearing impaired that both need and can afford hearing aids, the market penetration is only around 25%.
It would thus be desirable to provide apparatus, systems and methods for processing, transmitting and receiving control signals to and from personal communication devices; particularly, hearing devices, and devices employing same, that reduce or overcome one or more of the above noted drawbacks that are associated with conventional hearing devices.
It is therefore an object of the present invention to provide improved apparatus, systems and methods for processing, transmitting and receiving control signals to and from personal communication devices; particularly, hearing devices, and devices employing same that overcome one or more of the drawbacks that are associated with conventional hearing devices.
It is another object of the present invention to provide a highly asymmetrical or uni-directional communications system between a controlling device and at least one hearing aid device that is capable of executing a limited number of slow speed setting adjustments in a reliable manner without requiring complex transmission circuitry within the hearing aid devices.
It is another object of the present invention to further simplify the communications system described above by incorporating complex and reliable signaling protocols specifically designed to have the burden of the complexity encapsulated within the host device transceiver and the hearing aid receiver with the aim of greatly simplifying or completely eliminating the hearing aid transmitter element.
It is yet another object of the present invention to incorporate the operator's actions as a portion of the communications system with the aim of completely eliminating the hearing aid transmitter element, thereby significantly simplifying the hearing aid device and significantly reducing its power consumption.